Slab foundation building in Garden Grove CA - level and square, ready to frame on

A reinforced concrete slab in Orange County usually costs about $8 to $14 per square foot, and that's the going range in the area, not our price. A slab that needs a lot of soil replaced or extra steel from the engineer usually lands toward the higher end. My written estimate gives you the number for your own slab.

Most do, because Garden Grove requires a geotechnical investigation, a study of the soil on your lot, for every project except one-story additions, ADUs and detached structures up to 1,200 square feet. If your lot is in a designated flood zone, the report is required no matter the size. The city says all of Garden Grove lies in a liquefaction zone, which is ground that can lose strength in a strong earthquake, so it applies the same soil report rules across the city. On some projects, the city also calls for replacing the top layer of soil with clean compacted fill before trenching, and it wants a compaction certificate for that fill at the foundation inspection, so it's worth settling early who supplies it. You can check the city's soil report requirements to see where your project falls.

Expect some cracks, because steel inside a slab doesn't stop concrete from cracking, but reinforcement that's sized and placed right should keep the cracks tightly closed. A tight hairline crack is normal. A crack that opens wide or has one side higher than the other usually means something underneath has moved. Ask anyone bidding your job how they size the reinforcement and where it goes.

A slab should be walkable within 48 hours, though concrete takes 28 to 30 days to fully cure. To be safe, give it a week before heavier loads like stacked lumber or equipment go on it. Let your builder know those dates so deliveries line up.

The choice usually comes from your engineer, who works from the soils report on your lot. One trade group for post-tensioning says these slabs are a cost-efficient, high-performance choice for homes on shrink-swell soils, which swell when wet and shrink as they dry. Post-tensioned slabs are reinforced with steel cables that are pulled tight after the concrete hardens. The same group says they can often go in faster than a comparable rebar or wire mesh slab, because there are fewer pieces to handle and less concrete to place.

Start by checking that they hold a California contractor license for concrete, since the state's license classes define a concrete contractor as one who forms, pours, places, finishes and installs concrete work. Then ask who comes out to look at the job, how they prepare the base and how they check the steel before the pour, because those hidden steps decide how the slab holds up. We're licensed and fully insured, and I come out to look at your job myself.